Bruce found a photo (taken by Jim Walshe) of the mosaic of the Hip, Hip Hurra! painting:
For comparison, here is the original painting by Peder Kroyer:
Jim Walshe says about the mosaic: "A mosaic build organised by Warren Elsmore as part of the Visit Denmark exhibition in St Katharine's Dock, London. The picture is by Peder Kroyer and it's in the Skagen Museum in Denmark. The mosaic is going to the museum to be displayed with the original. The mosaic is made of 768 6x6 plates, making 27,648 studs in the picture."
I guess you really can call yourself a LEGO artist if you've got your art hanging in a museum!